Electrostatic controls



June 21, 1960 Original Filed July 2, 1954 J. w. DIESEL 2,942,077

ELECTROSTATIC CONTROLS 2 Sheets-Sheet 1 mum/r02: Jaw/v 1%.7/[554 a, y y6 June 21, 1960 J. w. DIESEL 2,942,077

ELECTROSTATIC CONTROLS Original Filed July 2, 1954 2 Sheets-Sheet 2 Id!IIIII /0 W F I 65 M United States Patent ELECTROSTATIC CONTROLS John W.Diesel, Maplewood, Mo., assignor to Erdco, Iuc., St. Louis, Mo., acorporation of Missouri Original application July 2, 1954, Ser. No.441,057. Divided and this application Oct. 28, 1957, Ser. No. 692,602

18 Claims. (Cl. 200-87) This invention relates generally toelectrostatics and more particularly to electrostatic controls, such asrelays, and is a division of my copending application, Serial No.441,057, filed July 2, 1954.

It has been known for many years that an attractive force is developedbetween two bodies when they bear opposite electric charges, but thecommercial applications of this principle have been few. Indeed, theelectrostatic controls heretofore proposed have been largely laboratorycuriosities of erratic performance and considerable complexity.Accordingly, it is an object of the invention to simplify theconstruction and improve the operation of electrostatic controls. Morespecificially, the invention provides electrostatic controls that arecomparable in function to electromagnetic and electronic devices, butwhich can be operated with better efficiency, manufactured atsubstantially less cost, made considerably more compact, and moreconveniently connected and assembled in multiple-component apparatus.

The construction of an electrostatic relay has presented seriousproblems to those skilled in the art. The electro. static or actuatingforces are quite weak and are extremely sensitive to plate spacing, withthe result that the performance is erratic and considerable precision isrequired in manufacture. If the plate spacing were slightly greater thanintended, the plates would fail to attract, and if too close, they wouldreadily be actuated by extraneous secondary effects, such as mightresult from leakage.

Attempts to resolve these difiiculties by the use of high voltage andclose spacing of the plates have not been too successful, because theylead to a considerable problem in preventing discharge between theplates, such discharge resulting in loss of the electrostatic force. Ithas, therefore, been suggested that the plates be protected againstdischarge with an intervening layer of solid insulation, but thisexpedient has led to even more serious difficulties. The introduction ofsolid insulation necessitates an increase in the distance between theconductive surfaces of the plates, which consequently weakens theelectrostatic force, and the insulation, if not of considerablethickness, is subject to breakdown under high voltage stresses. Moreimportant, however, are the problems that arise from dielectricabsorption and the property of the insulation to collect a surfacecharge, these factors causing the plates to stick and otherwisemisbehave. In some instances, the plates will fail to release uponremoval of the exciting voltage, and in other instances, the plates willmove in a direction opposite to that intended when excitation isapplied.

Accordingly, one of the objects of the present invention is to providean improved relay structure especially adapted for mnlti-componentapparatus. With such a relay, closed or open circuit conditions aredetermined more by the distance between the contacts rather than byactual engagement, and the behavior is more analogous to that of agas-filled tube than that of a solenoid relay. Such high voltages (whichin the case of a multicomponent apparatus would be of the same order of2,942,07i Patented June 21, 1960' ice magnitude as those used to excitethe plates) permit the v panel in response to the establishment of aclosed circuit condition, even though the contacts are not in perfectengagement, a feature which greatly facilitates manufacturing proceduresand improves reliability. Low current signals are desired, especiallywhen the contacts are small, in order to prevent heating to an extentsuch that an injurious arc effect is established by burning, melting orvaporization of the contacts. High-voltage low-current signals haveadditional advantages when the circuit components are formed by printedcircuit techniques.

One of the fundamental concepts of this invention is the use of highvoltage and close spacing of the plates, features which have heretoforebeen impractical, but for the introduction of a solid interveninginsulator for preventing discharge between the plates, which insulator,in turn, has resulted inadditional difiiculties of an even more seriousnature. The invention contemplates, in a preferred embodiment, thatthere will be no such solid insulator, but that neutralizing dischargebetween the plates will be controlled by high resistance within thecontrol itself. Preferably, one of the plates is formed, at least inpart, of high resistance material, and discharge is localized overcertain areas of the plates, the arrangement being such that other areasof the plates will be maintained at different potential, despite thepresence of a charge transfer. This arrangement serves to prevent theuncontrolled accumulation of charges of a type that would producemalfunctioning of the control, and also permits very close spacing ofthe plates.

Additionally, the invention contemplates the provision of a highresistance shorting connection between the plates, the arrangement beingsuch as to permit adequate accumulation plate excitation and yet quickremoval -of such charges in response to the withdrawal of the excitingvoltage. This shorting connection or release circuit has the additionalfunction of discriminating between true exciting signals and extraneouscharges resulting from leakage, which if permitted to accumulate, mightresult in false actuation of the control.

While the above principles might be utilized in a wide relatively fixedrigid member, whereas an opposite panelmay be mounted to flex toward andaway from the fixed presence and absence of plate excitation. The platesare formed on opposed faces of these panels as areas of the order of asquare inch, contacts being actuated by relative movement of the panels.

In one embodiment, the movable panel includes a flap, the free end ofwhich is normally spaced from the fixed panel so that the inherentresilience thereof supplies the bias for opening the contacts andseparating the plates. This flap is enclosed in a fixed frame-likespacer and is limited in outward movement by a fixed overlying shieldingpanel. A movable contact is secured at the free end of the fiap forcooperation with a fixed contact mounted over the panel, alow-resistance plate being formed by silver paint on the flap and ahigh-resistance coating being formed on the other With this arrangement,the free end portion of the movable plate is prevented from engaging thehigh-resistance fixed plate, although the plates may engage one anotherin their center portions. The exciting circuit lead for the free end ofthe flap. Leads for the movable contact and of charges on the plates inresponse to fixed panel with a carbon paint.

plate may extend on opposite faces of the flap to the fixed end thereof;anda high-resistance release circuit is provided for shorting theplates.

The terminals for the plates and contacts are brought out at the sidesand ends of the unit; and these terminals may extend across the edges ofthe unit in order to make connection with similar units stacked one'upon the other or with a suitable base upon which units are secured. Itwill be observed that this laminar panel construction simplifiesmanufacturing operations inasmuch as such panels may be readily 'diecut, printed and assembled with automatic machinery.

Other features of the invention will be in part apparent from and inpart pointed out in the following detail description taken in connectionwith the accOmPanying drawings, in which:

'Fig. l isan exploded view of certain insulating panels which areassembled to form arelay;

Fig. 2 is a view similar to that of Fig. 1, but showing the reversedfaces of-th'e insulating panels;

Fig. 3 is an enlarged sectional'view' of the assembled panels,thicknesses being exaggerated;

a Fig. 4 is a sectional view taken on the line 4-4 of Fig. 3;

'Fig. 5 is a similar section taken on the line 55 of Fig. 3;

Fig. 6 is a top plan view of a relay arm showing a construction for usewhere a relay is to control a large number of secondary circuits; and

Fig. 7 is a detailed sectional view illustrating an alternativeembodiment of the relay arm.

Reference is now made to Figs. 1-5 for a description of a specificstructure which might'bfe used as a relay in a digital computer andother rnulti-component apparatus. The device comprises a plurality offlat, generally rectangular insulating members for carrying theconductive elements. In a device for controlling ten secondary circuits,the panels measure approximately three inches in'width and length, andare of varying thickness and composition. A bottom panel 101 and toppanel 109 are .010 inch Vinylite (polymerized vinyl chloride resin) arelay-arm panel 105 is .005 inch Vinylite, a con tact member 103 is .020inch Vinylite, and a spacer frame 107 is .060 inch laminated phenolic orstyrene resin. Such insulating members would be die cut from sheetstock, the conductive elements being formed thereon using printed;circuit techniques. The coated members are thenassembled in stackedoverlying relationship and are secured together, as by bolts 111 throughcorner apertures 113.

"The panel 101 constitutes the base. of the device and servesas asupport for the fixed plate, which is formed as a coating 115 ofconductive paint. Conductive paints being known in the art, they are notdescribed other than to note that they customarily comprise a suspensionof conductive granules in a suitable binder. The resistance ofthe paintand resulting coating is to some extent controlled by the proportionsand character of the ingredients, silver granules being generally usedwhere high conductivity or low resistance is desired, and carbongranules being utilized for high resistance paint.

"In the disclosed embodiment, the fixed plate 115 is formed as a highresistance coating measuring one and three-eighths' inches in width andone and three-fourths inches in length, The paint is of a type providingapproximately one hundred seventy-five megohms per slquareinch, thisbeing a term of art indicating that a coating one inch in width andlength normally has a resistance'of the stated value between oppositeedges. The. plate area 115 extends close to an end 117 of the device anda high conductivity lead is formed as a strip l' l9"to extend acrossthat end of the plate to an adjacent corner aperture 113. A connectionto ground and to the negative terminal of the exciting source is thenmade through the associated bolt 111. i i

It may be observed at this point that the terms high resistance and highconductivity (or low resistance) are used ina relative sense inasmuch asprinted leads formed with silver paint will have appreciable resistance.It is only intended that the voltage drop in the leads are nominal inrelation to the drop at a resistive plate or across one of theresistances referred to. Also, a distinction is made between resistivematerial, such as carbon paint, and a semi-conductive dielectric, suchas stone organic membranes, the latter having only a very slight leakageusually aided by absorbed moisture. Semiconductive dielectrics areconsidered impractical because of their very high volume resistivity, ifsuch materials can really be considered to have a resistance.

The plate may in part extend beneath a thin piece 121 of insulatingmaterial, which is located at the end 117 of the device to minimizeleakage between the fixed plate and fixed contacts. This covered portionof the plate 115 serves as a plate series resistance. The resistor ofthe release circuit (as disclosed in the parent application) is arelatively narrow strip 123 of high-resistance conductive paintextending over the panel 101 outwardly of the plate 115 and inwardly ofthe side edge 125 of the device, and a lead 127 extends therefrom to theside 129 of the device. The width and length of this strip, as Well asthe character of the paint, determine the resistance in the releasecircuit, which could be approximately thirty megohms in the describedembodiment.

The contact member 103 has a central opening for accommodating the relayarm of the device, and upwardly-laoing contacts 131 are mounted alongthe margin of this opening and high-conductivity leads 1 33 extend tothe adjacent end 117 of the device. Although conductive paints may notbe entirely satisfactory for contact purposes, there are othertechniques known in the art which may be utilized in forming alightweight ccntac' which will withstand the slight heating to beexpected from sparking. Although some degree of uniformity is desiredwhen there are several contacts, the problem is not what it is inconventional deviceswhere wiping engagement isgenerally necessary toestablish a closed circuit condition and where contact rebound is amatter for concern.

The relay-arm panel 105 is out about the margins -1 7, 125 and 129 to'form a resilient flap 135, the free end of which extends over the fixedcontacts 131 as a relay arm. The movable plate is a high-conductivitycoating 137 over the lower face of the flap, the plate extending from apoint short of the free end to the other'end 139 of the device, where itis connected to a strip 141 of high-conductivity paint. The conductor141 extends over the fixed marginal portion of thepanel to the. side129, so as ultimately to make a connection with the lead 127 of therelease circuit.

Movable contacts 143 aremounted on the freeend of the flap forcooperation with the fixed contacts, and lead-formingv strips 145 ofhigh-conductivity paint extend over. the upper face of the flap to theend 139 of the device. Inasmuch as the flap isfiexed during use, it

may be desirable to incorporate, a plasticizer in thev conductive paintforming the coatings 137 and 145.

In assembly, anarrow piece ,147 of insulating material is sandwichedbetween the flap and the bottom panel 101 adjacent the fixed or hingedend so as to urge. the relay :arm 135 upwardly. Movement of the relayarm is accommodated by the surrounding frame-like spacer 107- and islimited by engagement with the, overlying top. panel 109. When severaldevices are to be stacked one:

upon the other, the; panel 109 may be-coated to shield the severaldevices against electrical interference with one another. Conductivestrips 149 on the, lower face. of

the panel 109 extend over the contact leads and are,

electrically connected thereto. at the end 139 of the device, whereas aconductive shield 151 on the upper face. of this panel is connected. tothe movable plate-by .a lead 153at theside129 of the device.

It will be noted that the free end portion of the flap 135 is projectedthrough the contact member 103 and is also curled outwardly somewhat,the latter being desirable in that it permits relatively close spacingof the plates 115 and 137 with rather wide spacing at the contacts.Contact closure is achieved both by downward movement of the flap and bya tendency of the flap to straighten under the electrostatic forcesapplied across the plates. The contact member 103 prevents the platesfrom coming into physical engagement over their entire surfaces,however. The inherent resiliency of the flap supplies the bias forotherwise opening the contacts and separating the plates, the wedgingstrip 147 being adjustable to vary the amount of bias, but in thefinished device, this wedging strip is secured so that the device may beoperated in any position.

The disclosed arrangement also provides for connection of the electricalelements merely by assembly of the panels. To that end, connectingelements of highconductivity paint are formed on the several insulatingmembers to extend across the edges thereof and partially over themargins. Connecting elements 155 provided at the side 129 are aligned sothat the leads 127, 141, and 153. become connected with one another whenthe members are assembled together. Connecting elements 157 are providedat the end 117 in alignment with the leads 133 for the fixed contacts.Similar connecting elements 159 located at the other end serve toconnect the leads 145 for the movable contacts and the overlyingcoextensive shielding strips 149. The arrangement is not only desirablein facilitating the construction of a single unit but also facilitatesthe assembly and connection of several units, whether they be stackedone upon the other or mounted on a panel previously ruled withconductive strips adapted to register with the connecting elements 155,157 and 159.

small expense in comparison to present devicm used for equivalentpurposes. The insulating members or panels can be die cut and coated athigh rates of production, and it is possible that conventional printingmachinery may be used for this purpose. Assembly of the panels isobviously a very simple operation, and the assembled units may bereadily stacked or mounted upon panels to form multiple-componentapparatus. The block-like shape and the small size of the units alsopermits a very compact arrangement.

Additionally, it is to be observed that the relay arm is entirelyenclosed in the device illustrated and described in connection withFigs. 1-3, and it will be apparent that the chamber containing the relayarm may be hermetically sealed to provide a controlled atmosphere. Suchan arrangement may be desired when high relative humidity producesleakage in excess of that which can be adequately handled by the device.A sealed condition is readily achieved by compressing the insulatingpanels or by coating the outer surface of the device with lacquer.

Having thus described the invention, what is claimed and desired to besecured by Letters Patent is:

1. In an electrostatic relay having a pair of opposedelectrostatically-actuated conductive plates, one of which Fig. 6illustrates an alternative arrangement which might be used where arather wide relay arm is required to accommodatea. large number ofsecondary circuits 245. In this instance, one or more slots 263 are cutin the center of the flap 235 to relieve buckling andfacilitate escapeof the air cushion between the plates as the relay arm is actuated.While there are no theoretical limits to the size of the relay arm,present experience seems to indicate that a relay arm one-eighth inch inwidth and one-half inch in length is about the smallest practical size,and a relay arm three inches in width and two inches in length is aboutthe largest useful size. These figures are given merely in the nature ofsuggestion, however, and should not be taken as limiting inasmuch asfurther development work may extend the range considerably.

Fig. 6 also illustrates an arrangement wherein the free end of the relayarm is slit at 265 to provide resilient contact fingers 267 carrying themovable contacts. In has been found that this type of relay arm isespecially desirable when a large number of secondary circuits arecarried on the relay arm.

It will additionally be apparent that normally-closed or double-throwrelays may be designed in accordance with the principles of thisinvention. For example, Fig. 7 illustrates a possible arrangement for adouble-throw relay. In this instance, the relay arm 305 has upper andlower movable plate areas 307. Movable contacts 309 are mounted at theend of the arm, but the lead 319 therefor is embedded in the relay armin insulated relationship from the plates 307, as by using a laminatedtype of construction. A pair of fixed contacts 303 are spaced onopposite sides of the movable contact 309, and resilient biasing fingers304 project inwardly from the fixed contacts so that the relay arm isnormally biased to a center position clear of the fixed plates 301 andfixed contacts 303.

From the foregoing, it will be apparent that the invention provides acontrol that can be manufactured at is movable toward and away from theother plate; the improvement comprising a movable relay arm formed froma thin sheet of plastic insulating material, and a relatively thinnercoating of conductive material adhered to one face over a wide area ofsaid insulating sheet to form said movable plate, said relay arm beingdisposed so that the conductive coating thereon faces the other platewithout an intervening solid dielectric.

2. In an electrostatic relay having a pair of opposedelectrostatically=actuated conductive plates, one of which is movabletoward and away from the other plate; the improvement comprising a firstrelatively rigid fixed panel of insulating material, a conductivecoating adhered to said first panel to form a fixed conductive plate, arelay arm formed by an overlying relatively flexible movable panel ofinsulating material, and a flexible coating of conductive materialadhered to said flexible panel to form the movable plate of the relay,said two coatings being disposed to face one another without anintervening solid dielectric.

3. An electrostatic relay as set forth in claim 2, wherein at least oneof said coatings is formed by carbon resistance paint.

4. In an electrostatic relay having a pair of opposed conductive plates,one of which is movable toward and away from the other plate; theimprovement comprising a relay arm formed from a thin resilientlyflexible panel of plastic insulating material, said panel having aconductivesurface forming the movable plate of the relay, said flexiblepanel being mounted with its conductive coating in opposednormally-spaced relationship to the other plate, said panel being atleast in part movable against the resilient bias of the panel toward theother plate under an electrostatic force developed between the twoplates.

5. In an electrostatic relay having a pair of opposed conductive plates,one of which is movable toward and away from the other plate; theimprovement comprising a relay arm panel of flexible plastic insulatingmaterial, a coating of conductive material secured to one surface ofsaid panel over less than the entire area thereof so as to form themovable plate, and a conductive contact element secured to said panel ofinsulating material in another area thereof so as to be in insulatedrelationship from the conductive plate-forming area thereon.

6. In an electrostatic relay having a pair of opposed conductive plates,one of which is movable toward and away from the other plate; theimprovement comprising a generally rectanguler relay-arm panel ofplastic sheet insulating material, said panel having conductive materialsecured to one face thereof to form the movable plate and being mountedso that a free end thereof is movable, a,

row of contacts mounted in spaced relationship from oneanother along thefree end margin of said panel, said contacts being in insulatedrelationship from one another and from the conductive plate-forming areaof the relayarm panel, and a second row of contacts fixed opposite saidfirst row of contacts for cooperation therewith.

7. An electrostatic relay as set forth in claim 6, further includingcontact leads extending across said relay-arm panel of insulatingmaterial from the contacts at the free end thereof toward the other endthereof, said contact leads being disposed on the surface of said panelopposite from that bearing the conductive plate-forming area.

8. An electrostatic relay as set forth in claim 6', where in saidmovable contact elements are formed as independently movable finger-likeprojections from the free end margin of the relay-arm panel.

9. An electrostatic relay as set forthin claim 7', wherein the relay armpanel further includes a second sheet of insulating material, said twosheets of insulatingdnaterial being secured together with the contactleads therebetween, and conductive plate-forming areas formed on the twoouter surfaces thereof.

10. An electrostatic relay comprising a pair of fixed rectangularpanels, spacer means sandwiched between opposite margins of said panelsto hold them in predetermined spaced generally-parallel relationship, arelayarm panel mounted to extend into the space between said fixedpanels, said relay-arm panel being in part movable toward and away fromone of said fixed panels, said relay arm panel having a conductiveplate-forming area on one face, the opposite fixed panel having aconductive plateforming area on its inner face, a movable contactmounted on the movable part of the relay-arm panel, and a fixed contactmounted in the space between said fixed panels for cooperation with themovable contact.

11. An electrostatic relay as set forth in claim 10, wherein said relayarm panel is formed of flexible sheet material, at least one end or" therelay-arm panel being secured in the spacer means along one margin ofthe relay.

12. An electrostatic relay as set forth in claim 10,

wherein one end of the relay arm is clear of the spacer means so as tobe movable between said fixed panels, and means interposed between themovable end only of the relay arm panel and the fixed panel with theconductive surface, thereby to prevent the movable end of the relay-armpanel from engaging said fixed panel.

13. An electrostatic relay as set forth in claim 10, wherein said spacermeans is a frame member formed with a rectangular center opening,thereby to enclose the plate-forming areas and contacts.

14. An electrostatic relay as set forth in claim 10,

wherein said panels and spacer means are formed of insulating material,the respective conductive plate-forms ing areas being formed byconductive coatings adhered thereto, and printed-circuit leads extendingfrom the plateforming areas to the margins of the respective panels be.tween the panels and spacer means sandwiched therebetween.

15. An electrostatic relay as set forth in claim 10, wherein saidrelay-arm panel is formed with a U-shaped cut which defines a flap, themargins of the relay-arm panel being secured by the spacer means andsaid flap being movable clear of said spacer means.

16. An electrostatic relay as set forth in claim 10', further includinga frame-like fixed-contact panel formed Witha rectangular centeropening, the fixed contact being mounted adjacent the opening on onemargin of} said contactpanel.

17.- An. electrostatic relay comprising a fixe ond ive plate, a movableconductive plate mounted, opposite the fixed plate and having a free endmovable toward and away from the fixed plate, contact means mounted foractuation by the free end of the movable plate, a plateenergizingconnection to the fixed plate at the end thereof adjacent the free endof the movable plate, a plate-energizing connection to the opposite endof the movable plate, and at least one of the plates being formed byresistive material.

18. An, electrostatic relay comprising a plurality of stacked panels, afirst one of said, panels being formed with a conductive plate-formingarea on its upper surface, a second superimposed panel, having a movablesection formed with a conductive plate-forming; area on its bottomsurface, and a third superimposed panel being formed as a spacer framewith a center opening for accommodating the movable section ofsaidsecond panel, and a fourth superimposed panel adapted to limitupward movement of? said movable, section of the second panel.

References (Iited in the file of this patent UNITED STATES PATENTS

